PicPrep for assistants

Connect your assistant to PicPrep, the desktop app that prepares photos for posting. With it, an assistant can open your projects, look at them, ask you questions in the app and make changes. Each change is applied by PicPrep, marked as the assistant's with its reason, and waits for you to keep or reject it. The judgement stays yours: the assistant cannot keep its own changes, answer its own questions, approve a slide, export, delete or change your settings.

This repository holds:

• picprep-mcp (packages/picprep-mcp/), the connector: a small program any MCP assistant runs as a local command (npx -y picprep-mcp). It finds PicPrep on your computer, starts it when it is not running, and passes messages between the assistant and the app. No dependencies.

• Skills (skills/), in the open Agent Skills format (SKILL.md): how to use each PicPrep stage well.

• Plugins and settings for each assistant, below.

You need PicPrep installed, and Node.js 18 or newer for npx (Claude Desktop's one-click bundle needs neither Node nor npx).

Set up your assistant

Related MCP server: SketchUp MCP

The tools

PicPrep gives an assistant eleven tools. They come from the app each time it runs, so this list is a description, not a definition: the app's own descriptions and schemas are what the assistant sees.

How it works

assistant ──stdio──> picprep-mcp ──HTTP, 127.0.0.1 only──> PicPrep app (POST /mcp)

1. The app writes its port and a random session token to state/server.json in its user folder each time it starts (macOS ~/Library/Application Support/picprep, Windows %APPDATA%\picprep, Linux ~/.config/picprep). A copy from before the rename from PhotoPrep keeps it in a folder called photoprep until the app has started once since; the connector reads it there.

2. picprep-mcp reads that file, checks the app answers on /health, and sends each message to the app's /mcp with the token. The tools, their descriptions and the instructions all come from the app, so a new PicPrep version brings its tools with it, with no connector update.

3. When the app is not running, the connector answers the assistant's opening handshake with the tool list the app gave last time (kept in state/mcp-catalogue.json), and starts the app only when a tool is actually called - so opening your editor does not open PicPrep. If the app was updated since, the assistant is told the tool list changed.

4. A PicPrep with no subscription or trial still answers the tools that only look; the others reply that only you can enter a licence, in Settings.

Where it starts the app from: macOS, the installed app (by its bundle id); Windows, %LOCALAPPDATA%\picprep\picprep.exe; Linux, /usr/bin/picprep (the .deb) or picprep on your PATH. Elsewhere, set PICPREP_APP to the app's executable in the assistant's server settings.

Nothing leaves your computer: the connector talks only to 127.0.0.1, and it writes one file (the tool-list cache).

When it does not connect

Run npx -y picprep-mcp --check. It says where it looks, whether PicPrep is running, and what it would start. The assistant is told in plain words too, and can tell you:

• PicPrep is not installed, or did not start: "PicPrep is not installed on this computer (looked for ...). Install it, open it once, then try again.", or that it was started but did not answer within 30 seconds.

• No project is open: "no PicPrep window has a project open ... Pass project (name or id)", with the projects there are. The assistant can open one for you.

• No subscription or trial: PicPrep still shows every project, and the tools that only look still answer. The ones that change something answer "PicPrep needs a subscription or an active trial (...). Only the person can enter one, in Settings → Licence."

Developing

npm test                     # plain Node, no packages
npm run build:mcpb           # dist/picprep.mcpb
node scripts/sync-skills.js  # copy skills/ from a checkout of the app next to this one
node test/parity.js --write  # record the app's tools again after they changed
node eval/eval.js labels     # the assistant eval's tasks and labels (EVAL.md says how it was run, and what it cost)

test/bridge.js runs the connector against a fake app (test/lib/fake-app.js) in a throwaway user folder; it never starts or touches a real PicPrep. test/plugin.js checks every manifest, skill and snippet, test/names.js that nothing here names a person or a private place, and test/parity.js that the tools this page and the skills describe are the app's.

With a checkout of the app beside this repo (a folder called picprep, or PICPREP_SRC), the tests also compare with the app itself: the connector's user folder is the app's on every OS, skills/ matches the app's, and the connector is run against the app's real server (no window, a throwaway user folder): it must list the app's tools unchanged, every tool is called once, and each refusal a new user meets must be a plain sentence. Without the checkout those checks say they were skipped. The app's source is not public; PicPrep's maintainers run them.

A skill describes tools the app serves: when a PicPrep release changes a tool, the skill that drives it changes in the same release. Every manifest (.claude-plugin/, .codex-plugin/, gemini-extension.json, mcpb/manifest.json) and packages/picprep-mcp/server.json carries the picprep-mcp version; bump them together. PUBLISHING.md says how a release goes out.

Licence

MIT. PicPrep itself is a separate, commercial app.